The invention described herein was made by employees of the United States Government and may be used by or for the Government for governmental purposes without payment of any royalties thereon or therefor.
The computer program listing appendix defined by a compact disc identified by the file name SIPS3D.TXT is herein incorporated by reference. The file SIPS3D.TXT has a file size of 78.3 kilobytes and a creation date of May 17, 2001.
1.0 Field of the Invention
This invention is related to a sound intensity prediction system and, more particularly, to a system that predicts the sound intensity created from a noise event and determines, on a three-dimensional basis taking into account cross winds and a moving noise source, the concentration of acoustic ray end points on land to indicate areas of noise intensification zones and where acoustic rays never touch down to indicate areas of quiet.
2.0 Description of Related Art
Several examples of a Sound Intensity Prediction System (SIPS) are known; one such SIPS is described in reports NSWCCD/TR-00/53 and NSWCDD 1TR-97/144. The SIPS described in these reports uses an acoustic ray tracing computer techniques to determine the locations of both noise enhancements and noise reductions related to noise events, such as explosive operations.
The SIPS serves as a noise-complaint management tool that takes into account the annoyance from a single noise event with respect to both the characteristics of the noise itself and on the community""s perception of the noise. Characteristics of the noise include: the intensity of the noise; its spectral characteristics; duration of the sound; the number of repetitions; the abruptness of onset or cessation; and background noise when a particular noise event occurs. Social surveys have found that community perception is driven by factors including: the degree of interference of the noise with activity; previous experience of the community with the particular noise; the time of day that the intruding noise occurs; fear of personal danger associated with the activities of the noise sources; socioeconomic status and education level of the community; and the extent the people believe that the noise output could be controlled.
The core of the SIPS described in the above-identified reports is a computer program that is based on a two-dimensional (2D) description of the atmosphere and topography. The two-dimensional SIPS utilize acoustic rays and the paths thereof in its prediction. Acoustic rays are mathematically traced in many directions around a sound source and are compiled into a map showing where the noise is likely to be distributed, its maximum levels, and its quiet zones. The prediction is then used to either proceed with an explosive event if quiet zones are predicted, or postponed if the two-dimensional SIPS show that the noise may impinge on a sensitive community and lead to complaints.
The two-dimensional SIPS includes hardware involved in not only the operation of the computer used in the prediction, but also in meteorological data collection system. As near as possible in both place and time to the explosive site, a RADIOSONDE is typically lofted by a weather balloon to gather temperatures, and wind speeds and directions at various altitudes. These three parameters versus altitude are input to the SIPS to make the predictions. The other source of input to the two-dimensional SIPS is a topographical description extracted from Level 1, Digital Terrain Elevation Data (DTED) produced by the National Imagery and Mapping Agency in Fairfax, Va.
The two-dimensional SIPS has served well its intended purpose. The predictions made by the two-dimensional SIPS have been accurate enough to allow a major disposal facility to avoid complaints from a number of noise events, e.g., explosion events. In spite of these successful operations, it is desired that further improvements be provided.
One drawback is that the two-dimensional SIPS considers the sound source, that is, the noise event, as having a stationary origin, which presents limitations in its usefulness. It is desired that a Sound Intensity Prediction System be provided that accommodates both stationary and moving sound sources.
Another drawback is that the topographical description input into the two-dimensional SIPS needs to consist of radial lines produced for each azimuth of interest related to the site of the noise event and needs to be produced from DTED prior to using the two-dimensional SIPS. It is desired that a SIPS be provided that uses the input topography description directly without the need for prior handling by the SIPS.
A further drawback is that the two-dimensional SIPS needs to simulate the atmosphere as a vertical sheet for each azimuth of interest related to the site of the noise event with all ray tracings remaining in that plane. The effects of cross winds can not be addressed with this technique. It is desired that a SIPS be provided that takes into account the effects of cross winds in its prediction.
Furthermore, one more drawback is that the two-dimensional SIPS can simulate sound reflections from ground surfaces in only a limited way since the reflected rays must also remain in the plane of interest. This limitation is relatively important since, under certain conditions, echoes may be responsible for very distant sound propagation in mountainous areas. It is desired that a SIPS be provided that can trace acoustic rays in all directions.
It is an object of the present invention to provide a Sound Intensity Prediction System (SIPS) that accommodates stationary and moving sound sources related to a noise event.
It is another object of the present invention to provide a SIPS that effectively utilizes topography descriptions directly.
It is a further object of the present invention to provide a SIPS that takes into account the effects of cross winds in its prediction.
Moreover, it is an object of the present invention to provide a SIPS that traces acoustic rays created by a noise event in all directions.
The invention is directed to a Sound Intensity Prediction System (SIPS) employing three-dimensional acoustic ray tracing techniques that take into account cross wind effects and handles stationary and/or moving sound sources serving as a noise event.
In one embodiment, a method for predicting is provided for determining the location of noise intensification zones and quiet zones created by a noise event emanating from a site of interest and generating acoustic rays. The method includes steps for providing a processor and inputting to the processor meteorological data collected at upper atmospheric layers over the site of interest. The meteorological data include temperatures, wind speeds and wind directions at the altitude of each of the atmospheric layers. The method further includes inputting a topographical description of the site of interest to the processor and providing a program for being run in the processor for tracing and calculating the acoustic ray paths through each atmospheric layer as a function of the altitude and taking into account the cross wind effect on the acoustic rays at each atmospheric layer.